You are wasting your time switching to pump then back to AVgas for many reasons.
1) Pump gas is like 93 AKI. 100LL (AVgas) is around 100AKI. So if your engine is setup up for running 100AKI fuel, running pump gas will not be good.
2) As Jerry stated, you will have to rejet.
3) Who ever told you AVgas is bad for your 2-stroke most likely has never ran it before.

Pick a fuel, pick a premix ratio and stick with it. Don't keep switching.

Also Jerry, my post about switching away wasn't directed to you.